DE102013105304A1 - Process for the preparation of a powdery precursor material, powdery precursor material and its use - Google Patents

Abstract

The invention relates to a process for producing a pulverulent precursor material of the following general composition I or II or III or IV: I: (CaySr1-y) AlSiN3: X1 II: (CabSraLi1-ab) AlSi (N1-cFc) 3: X2 III: Z5-δAl4-2δSi8 + 2δN18: X3 IV: (Z1-dLid) 5-δAl4-2δSi8 + 2δ (N1-xFx) 18: X4 with the process steps: A) producing a powdery mixture of educts, where the educts are ions of the above B) annealing of the mixture under a protective gas atmosphere, followed by milling, wherein in process step A) as starting material at least one silicon nitride having a specific surface area of greater than or equal to 5 m2 / g and less than or equal to 100 m2 / g, the annealing in step B) being carried out at a temperature of less than or equal to 1550 ° C.

Description

The invention relates to a method for producing a powdery precursor material, a powdery precursor material and the use of the pulverulent precursor material in an optoelectronic component.

In optoelectronic components, such as light emitting diodes (LEDs), ceramic materials or ceramic phosphors are used, which convert radiation emitted by a radiation source of a first wavelength into radiation having a second wavelength. The ceramic materials are characterized among other things by a high thermal load capacity due to their good heat dissipation. A ceramic precursor or phosphor precursor or precursor material requires a small particle size for high sinterability to easily subject it to ceramic processes such as tape casting or spark plasma sintering (SPS).

An object to be solved is to specify an improved method for producing a pulverulent precursor material. Other objects are to provide a powdery precursor material and its use. These objects are achieved by the subject matters with the features of the independent claims. Advantageous embodiments and further developments are the subject of the dependent claims.

• I: (Ca_ySr_1-y)AlSiN₃:X1
• II: (Ca_bSr_aLi_1-a-b)AlSi(N_1-cF_c)₃:X2
• III: Z_5-δAl_4-2δSi_8+2δN₁₈:X3
• IV: (Z_1-dLi_d)_5-δAl_4-2δSi_8+2δ(N_1-xF_x)₁₈:X4

In accordance with at least one embodiment, a method for producing a pulverulent precursor material is provided, which has the following general compositions I and / or II and / or III and / or IV:

• I: (Ca _y Sr _1-y ) Al Si ₃ : X1
• II: (Ca _b Sr _a Li _1-ab ) AlSi (N _{1 -c} F _c ) ₃ : X 2
• III: Z _5-δ Al _4-2δ Si _{8 + 2δ} N ₁₈ : _{X 3}
• IV: (Z _1-d Li _d ) _5-δ Al _4-2δ Si _{8 + 2δ} (N _{1 -x} F _x ) ₁₈ : X4

• A) Herstellen einer pulverförmigen Mischung von Edukten, wobei die Edukte Ionen der oben genannten Zusammensetzung I und/oder II und/oder III und/oder IV umfasst,
• B) Glühen der Mischung unter Schutzgasatmosphäre, anschließendes Mahlen, wobei im Verfahrensschritt A) als Edukt mindestens ein Siliziumnitrid mit einer spezifischen Oberfläche von größer oder gleich 5 m²/g und kleiner oder gleich 100 m²/g ausgewählt wird, wobei das Glühen im Verfahrensschritt B) bei einer Temperatur von kleiner oder gleich 1550 °C durchgeführt wird.

Where X1 and X2 and X3 and X4 are each an activator selected from the group of lanthanides, Mn ²⁺ and / or Mn ⁴⁺ ,
wherein Z is selected from the following group and combinations thereof: Ca, Sr, Mg
where 0 ≦ y ≦ 1 and 0 ≦ a <1 and 0 ≦ b <1 and 0 <c ≦ 1 and │δ│ ≦ 0.5 and 0 ≦ x <1 and 0 ≦ d <1. The method shows the following process steps:

• A) producing a pulverulent mixture of educts, where the educts comprises ions of the abovementioned composition I and / or II and / or III and / or IV,
• B) annealing the mixture under a protective gas atmosphere, then grinding, wherein in process step A) as the starting material at least one silicon nitride having a specific surface area greater than or equal to 5 m ² / g and less than or equal to 100 m ² / g is selected, wherein the annealing in Process step B) is carried out at a temperature of less than or equal to 1550 ° C.

X1 and / or X2 and / or X3 and / or X4 act here as activators or dopants. The activator can be incorporated into the crystal lattice of the cations of the powdery precursor material of the abovementioned general composition I or II or III or IV. The activator may comprise one or more elements from the group of lanthanides. Alternatively or additionally, the activator may be divalent manganese (Mn ²⁺ ) and / or tetravalent manganese (Mn ⁴⁺ ). The activator may be selected from a group comprising lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium. In particular, the activator is europium, cerium and / or lanthanum. When using trivalent elements as an activator, for example Ce ³⁺ , the charge neutrality is not given. Therefore, a charge compensation is usually necessary. The concentration of the activator in the powdery precursor material may be 0.1 to 20 mol%, especially 0.01 to 5 mol%, for example 0.5 mol%.

A protective gas atmosphere can be understood as meaning, for example, an inert or a reducing atmosphere. A reducing atmosphere does not exclude oxygen being present in this reducing atmosphere.

Under │δ│ ≤ 0.5, the range -0.5 ≤ δ ≤ 0.5 can be understood.

The annealed mixture can be sieved after grinding as needed.

With the above-mentioned method, particularly finely divided pulverulent precursor materials can be produced. The choice of suitable synthesis parameters and educts can influence the particle size or the particle size or the particle size value of the resulting pulverulent precursor material. In particular, the reactivity of the educts, for example, the nitrides used plays a role.

In method step A), according to one embodiment, silicon nitride (Si ₃ N ₄ ) and aluminum nitride (AlN) and / or calcium nitride (Ca ₃ N ₂ ) may be selected or used as the nitride. A crucial parameter for the reactivity of such nitrides is their specific surface area. The specific surface here means the surface of the material per weight unit. The specific surface area can be determined, for example, by gas adsorption (BET measurement).

The specific surface area of the silicon nitride is greater than or equal to 5 m ² / g and less than or equal to 100 m ² / g. In accordance with at least one embodiment, the specific surface area of at least the silicon nitride is selected from the range of 10 m ² / g to 30 m ² / g, for example 11 m ² / g. In particular, the specific surface area of silicon nitride is selected from a range of 10 to 15 m ² / g. In accordance with at least one embodiment, the specific surface area of aluminum nitride is selected from a range of 1 to 25 m ² / g, in particular 1 to 15 m ² / g, for example 3 m ² / g. The more reactive the nitride or nitrides used, for example silicon nitride, the lower the synthesis temperature can be selected and the more finely distributed is the precursor material produced. If the specific surface area is too high, for example greater than 100 m ² / g, there is a risk that the resulting pulverulent precursor materials sinter too much. In addition, there is a risk of oxide contamination due to the increased reactivity of the surface. The same applies to AlN from a specific surface area greater than 25 m ² / g.

In contrast to a coarse-grained precursor material, a finely divided and / or pulverulent precursor material here means that the precursor material has a low first grain size value d ₅₀ and / or a small second grain size value d ₉₀ . In particular, the first grain size value d _{50 has} a value less than or equal to 2 μm and / or the second grain size value d _{90 has} a value less than or equal to 3.5 μm.

In accordance with at least one embodiment, the starting materials can be weighed stoichiometrically in process step A). Alternatively, the reactants can also be weighed in non-stoichiometric, wherein at least one reactant or starting material can be weighed in excess, to compensate for any evaporation losses during production. For example, reactants comprising alkaline earth components can be weighed in excess. In accordance with at least one embodiment, in process step A), carbonates, oxides, nitrides, carbides, metals and / or halides are used as starting materials.

In this case, alkaline earth compounds or alkali metal compounds of alloy, hydrides, silicides, nitrides, halides, oxides, amides, amines, carbonates, metals and mixtures of these compounds and / or metals can be selected. Calcium nitride, strontium carbonate and / or strontium nitride are preferably used.

A silicon compound may be selected from silicon nitrides, alkaline earth silicides, silicon diimides, silicon hydrides, silicon oxide, silicon, or mixtures of these compounds and / or silicon. Preferably, silicon nitride is used which is stably readily available and inexpensive.

An aluminum compound may be selected from alloys, oxides, nitrides, metals and mixtures of these compounds and / or metals. Preferably, aluminum nitride is used, which is stably readily available and inexpensive.

Compounds from the group of lanthanides, for example compounds of europium, oxides, nitrides, halides, hydrides, metals or mixtures of these compounds and / or metals can be selected. Preference is given to using europium oxide, which is stable, readily available and inexpensive.

The bulk density of the educts is a measure of the particle size of the resulting precursor material. In process step A), particular care should be taken to ensure that the bulk density of the educts is low. The more compressed the pulverulent mixture of the educts in process step A), the coarser the resultant powdery precursor material becomes. On the other hand, a low bulk density leads to a finely distributed precursor material. The bulk density can be influenced by sieving.

In accordance with at least one embodiment, the silicon nitride in process step A) is partially crystalline or crystalline. Thus, a powdery finely divided precursor material can be produced. The crystallinity of the nitride has an influence on the particle size or grain size or grain size value of the pulverulent precursor material.

In accordance with at least one embodiment, a flux is additionally added in process step A). Alternatively, it is also possible to dispense with a flux in process step A). The flux can be used for improving the crystallinity and promoting the crystal growth of the powdery precursor material. On the other hand, the addition of the melting agent, the reaction temperature or annealing temperature can be reduced. The educts can be homogenized with the flux. Alternatively or additionally, the flux can also be added to the precursor material after the first annealing. The homogenization can be carried out, for example, in a mortar mill, a ball mill, a turbulent mixer, a flysch mixer or by other suitable methods.

In the method, method step B) can be carried out at least once. In particular, the method step B) can be carried out one to five times, in particular one to three times, for example twice. By the number of anneals, each with subsequent grinding and optionally screening the particle size or grain size or the grain size value of the resulting precursor material can be influenced. After the last annealing, the mixture is ground and sieved.

In the process, the annealing in process step B) is carried out at a temperature of less than or equal to 1550 ° C.

In accordance with at least one embodiment, process step B) is carried out at a temperature of 1200 to 1550 ° C., in particular 1200 to 1500 ° C., for example 1450 ° C. By selecting the temperature, the grain size or the grain size value of the resulting powdery precursor material can be influenced. The temperature here denotes the maximum temperature or the maximum synthesis temperature in process step B). The synthesis temperature chosen in this method is lower than those of conventional methods. The use of lower temperatures in process step B) leads to an improved sinterability when the powdery precursor material is further processed. Frequently, low synthesis temperatures in the case of nitride precursor materials or phosphors lead to the formation of secondary phases. By a suitable choice of reactive educts, the formation of secondary phases can be avoided despite a low synthesis temperature and a finely distributed precursor material can be obtained.

According to at least one embodiment, during the annealing in process step B), a hold time is selected, which is selected from the range of one minute to 24 hours. In particular, the hold time is selected from the range of one hour to eight hours, for example, in the range of one hour to four hours, for example, two hours. Holding time is the time during which the maximum temperature is maintained. Together with the heat-up and cool-down time, the hold time gives the total annealing time. With the holding time, the particle size of the resulting powdery precursor material can also be influenced.

Another parameter for influencing the particle size of the resulting powdery precursor material are the heating and cooling ramps. These can be selected, for example, depending on the type of furnace. An oven type is, for example, a tube furnace, a chamber furnace or a push-through furnace.

The annealing can be carried out in a crucible, for example, tungsten, molybdenum, aluminum oxide, graphite or boron nitride. In this case, the crucible may have a lining, for example of molybdenum or a lining of sapphire. The annealing may be done in a gas tight furnace under reducing atmosphere and / or inert gas, such as in hydrogen, ammonia, argon, nitrogen, or mixtures thereof. The atmosphere can be fluid or stationary. It may also be advantageous for the quality of the resulting precursor material if elemental carbon is present in finely divided form in the furnace chamber. Alternatively, it is possible to add carbon directly into the mixture of educts.

Multiple annealing of the reactants with or without intermediate post-processing such as milling and / or sieving can further enhance crystallinity or grain size distribution. Further advantages may be a lower defect density associated with improved optical properties of the resulting precursor material and / or a higher stability of the resulting precursor material.

In accordance with at least one embodiment, method step B) is followed by a method step C). In process step C), the pulverulent precursor material can be washed in caustic and / or acid. The acid may, for example, be selected from a group comprising hydrochloric acids, sulfuric acid, nitric acid, hydrofluoric acid, organic acids and mixtures thereof. The liquor may be selected from a group comprising potassium hydroxide, caustic soda and mixtures thereof. Such washes can increase the efficiency when preparing a doped powdered precursor material. Furthermore, as a result secondary phases, glass phases or other impurities can be removed and an improvement in the optical properties of the pulverulent precursor material can be achieved.

Furthermore, a powdery precursor material is produced, which is produced by a method according to the above statements.

In accordance with at least one embodiment, the powdery precursor material is characterized by a first grain size value d ₅₀ and / or a second grain size value d ₉₀ . In particular, the powdery precursor material has a first particle size value d ₅₀ and a second particle size value d ₉₀ . The first grain size value d ₅₀ may be less than or equal to 2 μm and / or the second grain size value d ₉₀ may be less than or equal to 3.5 μm. As the first particle size value d ₅₀ of the value of d, that 50% of the material obtained will be referred to, unless indicated otherwise, understood ₅₀ that is defined based on the volume fraction below and / or 50% of the material on the volume fraction above this size or this diameter is. Unless stated otherwise, the second particle size value d ₉₀ is defined here such that 90% of the material, based on the volume fraction, lies below and / or 10% of the material, based on the volume fraction, above this size or this diameter. The term grain size or grain size value in this context should include both the primary grain size of a single grain and the agglomeration grain size. The first or second grain size value can be determined by means of laser diffraction. The particle size can be described by the d ₅₀ and / or d ₉₀ value.

In accordance with at least one embodiment, the first grain size value d _{50 has} a value of 1 +/- 0.3 μm. Alternatively or additionally, the second grain size value d _{90 may have} a value of 3 +/- 0.3 μm.

The method thus provides a particularly finely distributed powdery precursor material which has both a very small first particle size value d ₅₀ and a second particle size value d ₉₀ . The finely divided pulverulent precursor material is suitable for use in optoelectronic components, such as light-emitting diodes. This includes both the use of the precursor in the form of powder as powdered conversion substance and the further processing of the precursor to ceramic phosphor converters or the use of these in optoelectronic components. The latter is mainly due to the good sinterability of the finely divided powdery precursor material.

Furthermore, the use of the pulverulent precursor material for forming at least one ceramic layer of an optoelectronic component is specified. The optoelectronic component can comprise, for example, an LED.

In accordance with at least one embodiment, the powdery precursor material forms a ceramic layer of an optoelectronic component, wherein the ceramic layer is arranged in the beam path of the optoelectronic component which has a semiconductor layer sequence.

According to this embodiment, the semiconductor materials occurring in the semiconductor layer sequence are not limited as long as they have at least partial electroluminescence. For example, compounds of the elements selected from indium, gallium, aluminum, nitrogen, phosphorus, arsenic, oxygen, silicon, carbon, and combinations thereof are used. However, other elements and additions may be used. The active region layer sequence may be based, for example, on nitride compound semiconductor materials. "Based on nitride compound semiconductor material" in the present context means that the semiconductor layer sequence or at least a part thereof, a nitride compound semiconductor material, preferably comprises or consists of Al _n Ga _m In _{1 nm} where 0 ≤ n ≤ 1, 0 ≤ m ≤ 1 and n + m ≤ 1. However, this material does not necessarily have to have a mathematically exact composition according to the above formula. Rather, it may, for example, have one or more dopants and additional constituents. For the sake of simplicity, however, the above formula contains only the essential constituents of the crystal lattice (Al, Ga, In, N), even if these can be partially replaced and / or supplemented by small amounts of further substances.

The semiconductor layer sequence can have as active region, for example, a conventional pn junction, a double heterostructure, a single quantum well structure (SQW structure) or a multiple quantum well structure (MQW structure). The semiconductor layer sequence can comprise, in addition to the active region, further functional layers and functional regions, for example p- or n-doped charge carrier transport layers, ie electron or hole transport layers, p- or n-doped confinement or cladding layers, buffer layers and / or electrodes and combinations it. Such structures concerning the active region or the further functional layers and regions are known to the person skilled in the art, in particular with regard to structure, function and structure, and are therefore not explained in any more detail here.

The powdery precursor material can completely form the ceramic layer. Alternatively, other additives which do not include the powdery precursor material may be incorporated in the ceramic layer. The powdery precursor material can be further processed into a ceramic or a ceramic layer. The ceramic processing can be done for example by spark plasma sintering (SPS) or tape casting.

In accordance with at least one embodiment, the ceramic layer is used as a wave conversion layer. The wave conversion layer can be contained in a light-emitting diode, for example a full-conversion light-emitting diode. Full conversion here and hereinafter means that the phosphor in the form of a powder or a ceramic layer is converted into the radiation of a semiconductor layer sequence, referred to herein as primary radiation, into a radiation having a different wavelength, referred to here as secondary radiation. Alternatively, the ceramic layer or the phosphor formed as a powder can only partially convert the primary radiation into secondary radiation. Partial means here that both primary radiation and secondary radiation emerge as total emission from the light emitting diode. In the wavelength conversion layer, it is therefore possible to use a powdery precursor material which is a phosphor precursor and has a small particle size and thus good sinterability. The use in a wavelength conversion layer can be carried out as a powder or as further processed ceramic. In both cases, the wavelength conversion layer can be arranged in the beam path of the light emitting diode and convert an emitted primary radiation partially or completely into a secondary radiation having a different, usually longer wavelength.

The wavelength conversion layer can be produced by the usual ceramic production methods as stated in connection with the powdery precursor material. In order to achieve a small particle size or grain size or particle size value of the pulverulent precursor material needed for the ceramic production process and the resulting increase in the sinterability, coarse-grained powder would have to be ground comparatively strongly. However, this leads inter alia to a poorer efficiency of the materials due to damage due to at least one grinding process and impurities that are introduced by the long grinding process in the millbase. This results among other things in a low quantum efficiency. Because the powdery precursor material is produced with reactive educts, it is already so finely distributed that longer grinding processes can be avoided. Therefore, the powdery precursor material can be processed into efficient ceramic wavelength conversion layers.

Alternatively, the powdery precursor material can be used without further processing to form a ceramic component as powdered conversion material in an optoelectronic component. For this purpose, the pulverulent precursor material can be processed in a volume casting. The powdery precursor material can be embedded in a matrix material, for example silicone or other suitable matrix materials. The powdery precursor material embedded in matrix material may be formed as a potting compound, layer or film.

According to at least one embodiment, the wavelength conversion layer is formed as a platelet, wherein the platelet is arranged directly on a main radiation side of the semiconductor layer sequence. The main radiation side here denotes a surface of the semiconductor layer sequence which is arranged transversely to the growth direction of the semiconductor layer sequence. "Direct" here and below means that the wavelength conversion layer is in direct mechanical contact with the main radiation side. In this case, no further layers and / or elements are arranged between the wavelength conversion layer and the main radiation side.

In accordance with at least one embodiment, the wavelength conversion layer completely converts the electromagnetic primary radiation emitted by the semiconductor layer sequence into an electromagnetic secondary radiation.

Alternatively, only one part of the wavelength conversion layer, for example 70%, converts the electromagnetic primary radiation emitted by the semiconductor layer sequence into an electromagnetic secondary radiation.

According to one embodiment, the wavelength conversion layer is in direct contact with the radiation source. Thus, the conversion of the electromagnetic primary radiation in the electromagnetic secondary radiation at least partially close to the radiation source, for example in a distance ceramic layer and radiation source of less than or equal to 200 microns, preferably less than or equal to 50 microns done (so-called "chip level conversion").

According to one embodiment, the wavelength conversion layer is spaced from the radiation source. Thus, at least in part, the conversion of the electromagnetic primary radiation into the electromagnetic secondary radiation can take place at a large distance from the radiation source. For example, in a distance between the ceramic layer and the radiation source of greater than or equal to 200 microns, preferably greater than or equal to 750 microns, more preferably greater than or equal to 900 microns (so-called "Remote Phosphor Conversion").

Herein and below, color terms with respect to emitting phosphors or precursor materials denote the respective spectral range of the electromagnetic radiation.

In accordance with at least one embodiment, the precursor material emits in the red spectral range. The red-emitting precursor material may be formed as a powder or ceramic. The red-emitting precursor material can be arranged in the beam path of an optoelectronic component.

In addition, the optoelectronic component may have a layer which emits in the yellow spectral range. The yellow-emitting layer may be formed as a powder or ceramic. The yellow-emitting layer can be arranged in the beam path of an optoelectronic component. In particular, yttrium aluminum garnet (YAG) and / or lutetium aluminum garnet (LuAG) may be used in one or as a yellow-emitting layer.

In accordance with at least one embodiment, a red and yellow-emitting layer is arranged in the beam path of the blue-emitting primary radiation in an optoelectronic component. The primary radiation is thereby only partially converted by the red and yellow-emitting layers, so that the total emission of the optoelectronic component is perceived by an external observer as warm-white light.

According to at least one embodiment, at least one additional phosphor or an additional precursor material is arranged in the beam path of the optoelectronic component based on the aforementioned embodiments. In principle, the additional phosphor or the additional precursor material can emit any wavelength from the visible spectral range. In particular, the additional phosphor or the additional precursor material emits in the blue spectral range (440 to 520 nm). The total emission of the optoelectronic component can be perceived as white light for an external observer.

According to at least one embodiment, the powdery precursor material is formed as a powder and arranged in an optoelectronic component. The powder is arranged in the beam path of the optoelectronic component which has a semiconductor layer sequence.

Further advantages and advantageous embodiments of the method, the powdery precursor material and its use will become apparent from the following embodiments and figures.

The 1 shows a first grain size value d ₅₀ and second grain size value d _{90 of} the powdery precursor material of embodiments and comparative examples, and

the 2 shows a schematic side view of an optoelectronic component according to an embodiment.

In the following, comparative examples V1, V2 and V3 for the production of a coarse-grained precursor material and exemplary embodiments A1, A2 and A3 for the production of finely divided pulverulent precursor materials are indicated.

Comparative Example C1: Preparation of CaAlSiN ₃ : Eu

50 g of Ca ₃ N ₂ , 41 g of AlN, 47 g of Si ₃ N ₄ (specific surface area about 11 m ² / g) and 5 g of Eu ₂ O ₃ are weighed in under a protective gas atmosphere and homogenized. Subsequently, the educt mixture is slightly densified for several hours under a reducing atmosphere in the tube or chamber furnace at temperatures between 1550 ° C and 1800 ° C annealed. Subsequently, further annealing to adjust the grain size or the grain size value, also under reducing atmosphere, between 1550 ° C and 1800 ° C take place. After subsequent grinding and sieving of the annealing cake results in a coarse-grained phosphor having the general formula CaAlSiN ₃ : Eu. The in 1 and coarse-grained phosphor shown in Table 1 has, after work-up, a first grain size value d ₅₀ of 9.4 μm and a second grain size value d ₉₀ of 15.8 μm.

Comparative Example C2 Preparation of CaAlSiN ₃ : Eu

50 g of Ca ₃ N ₂ , 41 g of AlN, 47 g of amorphous Si ₃ N ₄ (specific surface area about 110 m ² / g) and 5 g of Eu ₂ O ₃ are weighed in under a protective gas atmosphere and homogenized. Subsequently, the educt mixture is slightly compacted for several hours under reducing atmosphere in the tube or chamber furnace at temperatures between 1300 ° C and 1800 ° C, for example, annealed at 1450 ° C. Subsequently, further annealing to adjust the grain size or the grain size value, also under reducing atmosphere, between 1300 ° C and 1800 ° C, for example at 1450 ° C take place. After subsequent grinding and sieving of the annealing cake results in a coarse-grained phosphor.

Comparative Example C3: Preparation of CaAlSiN ₃ : Eu

50 g of Ca ₃ N ₂ , 41 g of AlN, 47 g of amorphous Si ₃ N ₄ (specific surface area about 103 to 123 m ² / g) and 5 g of Eu ₂ O ₃ are weighed out under inert gas atmosphere and homogenized. Subsequently, the educt mixture is slightly compacted for several hours under reducing atmosphere in the tube or chamber furnace at temperatures between 1300 ° C and 1800 ° C, for example, annealed at 1450 ° C. Subsequently, further annealing to adjust the grain size or the grain size value, also under reducing atmosphere, between 1300 ° C and 1800 ° C, for example at 1450 ° C take place. After subsequent grinding and sieving of the annealing cake results in a coarse-grained phosphor. The coarse-grained phosphor has a first grain size value d ₅₀ of 2.3 μm and a second grain size value d ₉₀ of 4.9 μm ( 1 and Table 1).

Exemplary embodiment A1: Preparation of CaAlSiN ₃ : Eu

82 g of Ca ₃ N ₂ , 68 g of AlN, 78 g of Si ₃ N ₄ (specific surface area about 11 m ² / g) and 1 g of Eu ₂ O ₃ are weighed in under a protective gas atmosphere and homogenized. Subsequently, the starting material mixture is slightly densified for several hours under a reducing atmosphere in the tube or chamber furnace at temperatures between 1300 ° C and 1550 ° C annealed. After subsequent grinding and sieving of the annealing cake results in a fine-grained and very reactive powdery precursor material. This precursor material can be used for ceramic materials. In addition to the phase CaAlSiN ₃ : Eu, this powdery precursor material consists of the intermediate CaSiN ₂ : Eu and still unreacted AlN. The latter convert completely to the desired CaAlSiN ₃ : Eu in ceramic production.

Exemplary embodiment A2: Preparation of CaAlSiN ₃ : Eu

82 g of Ca ₃ N ₂ , 68 g of AlN, 78 g of Si ₃ N ₄ (specific surface area about 13 m ² / g) and 1 g of Eu ₂ O ₃ are weighed in under a protective gas atmosphere and homogenized. Subsequently, the educt mixture is slightly compressed for several hours under reducing atmosphere in the tube or chamber furnace at temperatures between Annealed at 1300 ° C and 1550 ° C. After subsequent grinding and sieving of the annealing cake results in a fine-grained and reactive CaAlSiN ₃ : Eu. The pulverulent precursor material has a first particle size value d ₅₀ of 1.2 μm and a second particle size value d ₉₀ of 2.9 μm. X-ray diffraction (XRD) confirms the phase purity of the powdery precursor material.

Exemplary embodiment A3: Preparation of CaAlSiN ₃ : Eu

82 g of Ca ₃ N ₂ , 68 g of AlN, 78 g of Si ₃ N ₄ (specific surface area about 14 m ² / g) and 1 g of Eu ₂ O ₃ are weighed in under a protective gas atmosphere and homogenized. Subsequently, the starting material mixture is slightly densified for several hours under a reducing atmosphere in the tube or chamber furnace at temperatures between 1300 ° C and 1550 ° C annealed. After subsequent grinding and sieving of the annealing cake results in a fine-grained and reactive CaAlSiN ₃ : Eu. The pulverulent precursor material has a first particle size value d ₅₀ of 1.3 μm and a second particle size value d ₉₀ of 3.3 μm. X-ray diffraction (XRD) confirms the phase purity of the powdery precursor material.

The 1 shows the corresponding Comparative Examples V1, V2-1, V2-2 and V3 and the embodiments A1-1, A1-2, A2 and A3 is a graphical representation of a first grain size value d ₅₀ in microns and second grain size value d ₉₀ in microns with a corresponding hold time t in hours h, maximum temperature or maximum annealing temperature T _max in ° C and specific surface area A of Si ₃ N ₄ in m ² / g. Table 1 also shows the quantum efficiency QE in% of the pulverulent precursor material. Comparative Examples V2-1, V2-2 were prepared analogously to Comparative Example C2, the parameters such as the specific surface area A of Si ₃ N ₄ in m ² / g, maximum annealing temperature T _max in ° C and / or the maximum holding time t in h, according to Table 1 were set. In the embodiments A1-1 and A1-2 was analogous procedure. Table 1 also shows the first grain size value d ₅₀ in μm, the second grain size value d ₉₀ in μm and the quantum efficiency QE in% of the pulverulent precursor material according to an embodiment and of comparative examples. The QE was determined by powder tablet measurement. A in m ² / g T _max in ° C t in h d ₅₀ in μm d ₉₀ in μm QE in% V1 11 1580 4 9.4 15.8 83 V2-1 110 1550 4 5.8 16.1 69 V2-2 110 1,450 4 2.0 4.6 67 V3 103 to 123 1,450 2 2.3 4.9 51 A1-1 11 1,450 4 1.4 3.3 77 A1-2 11 1,450 2 1.1 3.0 68 A2 13 1,450 2 1.2 2.9 70 A3 14 1,450 2 1.3 3.3 70

From Table 1 it can be seen that when using a Si ₃ N ₄ having a specific surface area of greater than or equal to 5 m ² / g and less than or equal to 100 m ² / g as starting material and a temperature during annealing in step B) of less than or equal to 1550 ° C, a finely divided powdered precursor material can be produced which has a very low first particle size value d ₅₀ and / or a second particle size value d ₉₀ with correspondingly high quantum efficiency. The hold time is low and is between 2 and 4 hours.

Table 2 below shows the influence of the specific surface AA of aluminum nitride AlN in m ² / g on the first grain size value d ₅₀ and second grain size value d _{90 of} the finely divided powdery precursor material. The specific surface area of about 11 m ² / g of silicon nitride was kept constant in all experiments. Table 2 shows that a small specific surface area of aluminum nitride, in particular a specific surface area of ≦ 3.6 m ² / g, leads to small particle sizes or particle size values. For example, a powdery precursor material made with an aluminum nitride having a specific surface area of 3.1 to 3.6 m ² / g shows a first grain size value d ₅₀ of 1.1 μm and a second grain size value d ₉₀ of 3.9 microns. AA in m ² / g T _max in ° C t in h d ₅₀ in μm d ₉₀ in μm 3.1 to 3.6 1,450 2 1.1 3.0 > 115 1,450 2 4.3 17.8 2.3 to 2.9 1,450 2 1.4 4.2

It could be shown that due to the low specific surface area of the nitrides (educts) and the suitably selected temperature, a pulverulent precursor material can be produced in a targeted manner and controlled in its sintering properties or its surface. This gives rise to the possibility, in addition to the particle size, of influencing the packing density, for example in tape casting. In general, precursors with a high d ₉₀ value or second particle size value are difficult or impossible to process.

2 shows a schematic side view of an optoelectronic device 100 on the embodiment of a light emitting diode (LED). The optoelectronic component 100 has a layer sequence 1 with an active area (not explicitly shown), a first electrical connection 2 , a second electrical connection 3 , a bonding wire 4 , a casting 5 , a housing wall 7 , a housing 8th , a recess 9 , a precursor material 6 to form a ceramic layer 11 or wavelength conversion layer 11 , and a matrix material 10 on. The layer sequence 1 with an active region containing the wavelength conversion layer 11 is within the optoelectronic device, the encapsulation 5 and / or the recess 9 arranged. The first and second electrical connection 2 . 3 are under the layer sequence 1 arranged with an active area. An indirectly and / or directly direct electrical and / or mechanical contact, the layer sequence 1 with an active area and the bonding wire 4 and the layer sequence 1 with an active area with the first and / or the second electrical connection 2 . 3 on.

Furthermore, the layer sequence 1 be arranged with an active area on a support (not shown here). A carrier can be, for example, a printed circuit board (PCB), a ceramic substrate, a printed circuit board or a metal plate, eg aluminum plate.

Alternatively, a carrierless arrangement of the layer sequence 1 possible with so-called thin-film chips.

The active region is suitable for emitting electromagnetic primary radiation in a direction of emission. The layer sequence 1 for example, with an active region may be based on nitride compound semiconductor material. Nitride compound semiconductor material emits in particular electromagnetic primary radiation in the blue and / or ultraviolet spectral range. In particular, InGaN may be used as a nitride compound semiconductor material having an electromagnetic primary radiation having a wavelength of 460 nm.

In the beam path of the electromagnetic primary radiation is the wavelength conversion layer 11 arranged. The matrix material 10 is for example polymer or ceramic material. Here is the wavelength conversion layer 11 directly in direct mechanical and / or electrical contact on the layer sequence 1 arranged with an active area.

Alternatively, other layers and materials, such as the potting, between the wavelength conversion layer and the layer sequence 1 be arranged (not shown here).

Alternatively, the wavelength conversion layer 11 indirectly or directly on the housing wall 7 a housing 8th be arranged (not shown here).

Alternatively, it is possible that the precursor material is embedded in a potting compound (not shown here) and together with the matrix material 10 as casting 5 is formed.

The wavelength conversion layer 11 at least partially converts the electromagnetic primary radiation into an electromagnetic secondary radiation. For example, the electromagnetic primary radiation is emitted in the blue spectral range of the electromagnetic radiation, wherein at least part of this electromagnetic primary radiation from the wavelength conversion layer 11 is converted into an electromagnetic secondary radiation in the red and / or green spectral range and / or combinations thereof. The total radiation emerging from the optoelectronic component is a superimposition of blue emitting primary radiation and red and green emitting secondary radiation, the total emission visible to the external observer being white light.

The wavelength conversion layer 11 can be formed as a ceramic or powder and completely convert the electromagnetic primary radiation into electromagnetic secondary radiation. The electromagnetic secondary radiation has a red spectral range.

In accordance with at least one embodiment, the red-emitting wavelength conversion layer is 11 formed as a ceramic and additionally arranged with a formed as a powder yellow and / or green-emitting phosphor in an optoelectronic device. In particular, the optoelectronic component has a total emission, which is perceived as white light for an external observer.

In accordance with at least one embodiment, the red-emitting wavelength conversion layer is 11 formed as a ceramic and additionally or alternatively arranged with a formed as a ceramic yellow and / or green-emitting phosphor in an optoelectronic device. In particular, the optoelectronic component has a total emission, which is perceived as white light for an external observer.

In accordance with at least one embodiment, the red-emitting wavelength conversion layer is 11 formed as a powder and additionally arranged with a shaped as a ceramic yellow and / or green-emitting phosphor in an optoelectronic device. In particular, the optoelectronic component has a total emission, which is perceived as white light for an external observer.

In accordance with at least one embodiment, the red-emitting wavelength conversion layer is 11 formed as a powder and additionally arranged with a formed as a powder yellow and / or green-emitting phosphor in an optoelectronic device. In particular, the optoelectronic component has a total emission, which is perceived as white light for an external observer.

In accordance with at least one embodiment, the primary radiation has a wavelength from the UV spectral range. The wavelength conversion layer 11 may be formed as a ceramic or powder and additionally be arranged in an optoelectronic component with a formed as a ceramic or powder yellow and / or green-emitting phosphor and formed as a ceramic or powder blue-emitting phosphor. In particular, the optoelectronic component has a total emission, which is perceived as white light for an external observer.

The invention is not limited by the description with reference to the embodiments, but the invention includes any novel feature and any combination of features, which in particular includes any combination of features in the claims, even if this feature or combination itself is not explicitly in the claims or Embodiments is given.

Claims (18)

Process for the preparation of a pulverulent precursor material of the following general composition I or II or III or IV: I: (Ca _y Sr _1-y ) AlSiN ₃ : X ₁ II: (Ca _b Sr _a Li _1-ab ) AlSi (N _1-c F _c ): _{X 2} III: Z _5-δ Al _4-2δ Si _{8 + 2δ} N ₁₈ : _{X 3} IV: (Z _1-d Li _d ) _5-δ Al _4-2δ Si _{8 + 2δ} (N _{1 -x} F _x ) ₁₈ : X4 wherein X1 and X2 and X3 and X4 are each an activator, wherein the activator is selected from the group of the lanthanides, Mn ²⁺ and / or Mn ⁴⁺ , where Z is selected from the following group and combinations thereof: Ca, Sr, Mg where 0 ≦ y ≦ 1 and 0 ≦ a <1 and 0 ≦ b <1 and 0 <c ≦ 1 and │δ│ ≦ 0.5 and 0 ≦ x <1 and 0 ≦ d < 1, with the process steps A) producing a powdery mixture of educts, wherein the educts ions of the above compositions I and / or II and / or III and / or IV, B) annealing of the mixture under a protective gas atmosphere, then grinding, wherein in Process step A) as starting material at least one silicon nitride having a specific surface area of greater than or equal to 5 m ² / g and less than or equal to 100 m ² / g is selected, wherein the annealing in step B) at a temperature of less than or equal to 1550 ° C is performed.  A method according to the preceding claim, wherein the annealing in step B) is carried out at a temperature selected from the range of 1200 ° C to 1550 ° C. Method according to one of the preceding claims, wherein the silicon nitride has a specific surface area in the range of 10 m ² / g to 30 m ² / g. Method according to one of the preceding claims, wherein in process step A) as starting material AlN is selected, wherein AlN has a specific surface area of 1 to 25 m ² / g.  Method according to one of the preceding claims, wherein in process step A) as starting materials carbonates, oxides, nitrides, carbides, metals and / or halides are used.  Method according to one of the preceding claims, wherein in step A) at least the silicon nitride is partially crystalline or crystalline.  Method according to one of the preceding claims, wherein the method step B) is carried out one to five times.  Method according to one of the preceding claims, wherein during the annealing in step B) a holding time is selected, which is selected from the range of 1 minute to 24 hours.  Method according to one of the preceding claims, wherein in a subsequent to step B) process step C) the powdery precursor material is washed in caustic and / or acid.  A powdery precursor material produced by a process according to any one of claims 1 to 9. A powdery precursor material having a first grain size value d ₅₀ and a second grain size value d ₉₀ , the first grain size value d _{50 being} less than or equal to 2 μm and / or the second grain size value d _{90 being} less than or equal to 3.5 μm. Powdery precursor material according to the preceding claim, wherein the first grain size value d _{50 has} a value of 1 ± 0.3 μm and / or the second grain size value d _{90 has} a value of 3 ± 0.3 μm. Use of a pulverulent precursor material according to claim 10 or 11 or 12 for the formation of a ceramic layer ( 11 ) of an optoelectronic component ( 100 ), wherein the ceramic layer ( 11 ) in the beam path of the optoelectronic component, which has a semiconductor layer sequence ( 1 ) is arranged. Use according to claim 13, wherein the ceramic layer ( 11 ) is used as the wavelength conversion layer. Use according to the preceding claim, wherein the wavelength conversion layer is formed as a platelet, wherein the platelet is deposited directly on a main radiation side of the semiconductor layer sequence ( 1 ) is arranged. Use according to claim 14, wherein the wavelength conversion layer comprises that of the semiconductor layer sequence ( 1 ) completely converted electromagnetic primary radiation into an electromagnetic secondary radiation.  Use according to claim 13, wherein at least one additional phosphor or an additional precursor material is arranged in the beam path of the optoelectronic component for generating white light. Use of a pulverulent precursor material according to claim 13 in an optoelectronic component ( 100 ), wherein the powdery precursor material is formed as a powder, wherein the powder in the beam path of the optoelectronic component, which has a semiconductor layer sequence ( 1 ) is arranged.

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